Java java.awt Class CheckboxMenuItem（JDK8）

Constructor Detail

• CheckboxMenuItem

  public CheckboxMenuItem()
                   throws HeadlessException

  Create a check box menu item with an empty label. The item's state is initially set to "off."

  Throws:

  HeadlessException - if GraphicsEnvironment.isHeadless() returns true

  Since:

  JDK1.1

  See Also:

  GraphicsEnvironment.isHeadless()

• CheckboxMenuItem

  public CheckboxMenuItem(String label)
                   throws HeadlessException

  Create a check box menu item with the specified label. The item's state is initially set to "off."

  Parameters:

  label - a string label for the check box menu item, or null for an unlabeled menu item.

  Throws:

  HeadlessException - if GraphicsEnvironment.isHeadless() returns true

  See Also:

  GraphicsEnvironment.isHeadless()

• CheckboxMenuItem

  public CheckboxMenuItem(String label,
                          boolean state)
                   throws HeadlessException

  Create a check box menu item with the specified label and state.

  Parameters:

  label - a string label for the check box menu item, or null for an unlabeled menu item.

  state - the initial state of the menu item, where true indicates "on" and false indicates "off."

  Throws:

  HeadlessException - if GraphicsEnvironment.isHeadless() returns true

  Since:

  JDK1.1

  See Also:

  GraphicsEnvironment.isHeadless()

Method Detail

• addNotify

  public void addNotify()

  Creates the peer of the checkbox item. This peer allows us to change the look of the checkbox item without changing its functionality. Most applications do not call this method directly.

  Overrides:

  addNotify in class MenuItem

  See Also:

  Toolkit.createCheckboxMenuItem(java.awt.CheckboxMenuItem), Component.getToolkit()

• getState

  public boolean getState()

  Determines whether the state of this check box menu item is "on" or "off."

  Returns:

  the state of this check box menu item, where true indicates "on" and false indicates "off"

  See Also:

  setState(boolean)

• setState

  public void setState(boolean b)

  Sets this check box menu item to the specified state. The boolean value true indicates "on" while false indicates "off."

  Note that this method should be primarily used to initialize the state of the check box menu item. Programmatically setting the state of the check box menu item will not trigger an ItemEvent. The only way to trigger an ItemEvent is by user interaction.

  Parameters:

  b - true if the check box menu item is on, otherwise false

  See Also:

  getState()

• getSelectedObjects

  public Object[] getSelectedObjects()

  Returns the an array (length 1) containing the checkbox menu item label or null if the checkbox is not selected.

  Specified by:

  getSelectedObjects in interface ItemSelectable

  See Also:

  ItemSelectable

• addItemListener

  public void addItemListener(ItemListener l)

  Adds the specified item listener to receive item events from this check box menu item. Item events are sent in response to user actions, but not in response to calls to setState(). If l is null, no exception is thrown and no action is performed.

  Refer to AWT Threading Issues for details on AWT's threading model.

  Specified by:

  addItemListener in interface ItemSelectable

  Parameters:

  l - the item listener

  Since:

  JDK1.1

  See Also:

  removeItemListener(java.awt.event.ItemListener), getItemListeners(), setState(boolean), ItemEvent, ItemListener

• removeItemListener

  public void removeItemListener(ItemListener l)

  Removes the specified item listener so that it no longer receives item events from this check box menu item. If l is null, no exception is thrown and no action is performed.

  Refer to AWT Threading Issues for details on AWT's threading model.

  Specified by:

  removeItemListener in interface ItemSelectable

  Parameters:

  l - the item listener

  Since:

  JDK1.1

  See Also:

  addItemListener(java.awt.event.ItemListener), getItemListeners(), ItemEvent, ItemListener

• getItemListeners

  public ItemListener[] getItemListeners()

  Returns an array of all the item listeners registered on this checkbox menuitem.

  Returns:

  all of this checkbox menuitem's ItemListeners or an empty array if no item listeners are currently registered

  Since:

  1.4

  See Also:

  addItemListener(java.awt.event.ItemListener), removeItemListener(java.awt.event.ItemListener), ItemEvent, ItemListener

• getListeners

  public <T extends EventListener> T[] getListeners(Class<T> listenerType)

  Returns an array of all the objects currently registered as FooListeners upon this CheckboxMenuItem. FooListeners are registered using the addFooListener method.

  You can specify the listenerType argument with a class literal, such as FooListener.class. For example, you can query a CheckboxMenuItem c for its item listeners with the following code:

  ItemListener[] ils = (ItemListener[])(c.getListeners(ItemListener.class));

  If no such listeners exist, this method returns an empty array.

  Overrides:

  getListeners in class MenuItem

  Parameters:

  listenerType - the type of listeners requested; this parameter should specify an interface that descends from java.util.EventListener

  Returns:

  an array of all objects registered as FooListeners on this checkbox menuitem, or an empty array if no such listeners have been added

  Throws:

  ClassCastException - if listenerType doesn't specify a class or interface that implements java.util.EventListener

  Since:

  1.3

  See Also:

  getItemListeners()

• processEvent

  protected void processEvent(AWTEvent e)

  Processes events on this check box menu item. If the event is an instance of ItemEvent, this method invokes the processItemEvent method. If the event is not an item event, it invokes processEvent on the superclass.

  Check box menu items currently support only item events.

  Note that if the event parameter is null the behavior is unspecified and may result in an exception.

  Overrides:

  processEvent in class MenuItem

  Parameters:

  e - the event

  Since:

  JDK1.1

  See Also:

  ItemEvent, processItemEvent(java.awt.event.ItemEvent)

• processItemEvent

  protected void processItemEvent(ItemEvent e)

  Processes item events occurring on this check box menu item by dispatching them to any registered ItemListener objects.

  This method is not called unless item events are enabled for this menu item. Item events are enabled when one of the following occurs:

  • An ItemListener object is registered via addItemListener.
  • Item events are enabled via enableEvents.

  Note that if the event parameter is null the behavior is unspecified and may result in an exception.

  Parameters:

  e - the item event

  Since:

  JDK1.1

  See Also:

  ItemEvent, ItemListener, addItemListener(java.awt.event.ItemListener), MenuItem.enableEvents(long)

• paramString

  public String paramString()

  Returns a string representing the state of this CheckBoxMenuItem. This method is intended to be used only for debugging purposes, and the content and format of the returned string may vary between implementations. The returned string may be empty but may not be null.

  Overrides:

  paramString in class MenuItem

  Returns:

  the parameter string of this check box menu item

• getAccessibleContext

  public AccessibleContext getAccessibleContext()

  Gets the AccessibleContext associated with this CheckboxMenuItem. For checkbox menu items, the AccessibleContext takes the form of an AccessibleAWTCheckboxMenuItem. A new AccessibleAWTCheckboxMenuItem is created if necessary.

  Specified by:

  getAccessibleContext in interface Accessible

  Overrides:

  getAccessibleContext in class MenuItem

  Returns:

  an AccessibleAWTCheckboxMenuItem that serves as the AccessibleContext of this CheckboxMenuItem

  Since:

  1.3